Documents hold information and transferring documents transfers information. One of the problems with standard documents is that anyone obtaining the document, or a copy of the document, gains access to the information. The solution to this problem has been to encrypt documents or parts of documents. The encrypted information could be recovered with a key. In the loosest sense, a key is a piece of information that is used to decrypt encrypted information. In the past, the key was an algorithm or recipe. Modernly, encryption and decryption algorithms are widely known and the key is a very large number. Those skilled in the arts of encryption or secure communications are aware of a large number of encryption and decryption techniques and algorithms.
There are a variety of ways to include encrypted information in a document. One method is to simply encrypt the information and then print it as ciphertext. A bar code can be used. Steganography, in which information is hidden in a document, can also be used. Dataglyphs®, from Xerox, or similar technologies can be used to embed information in an image.
A receiver can't decrypt encrypted information without the key. As such, keys must be distributed. Keys and encrypted information must be distributed separately because anyone who has both can obtain the information. As such, various key exchange methodologies have been implemented. Key exchange methodologies are used to distribute keys. Those skilled in the arts of encryption or secure communications are aware of a large number of key exchange methodologies. For example, certificate authorities such as VeriSign and Thawte disseminate encryption and decryption keys to Internet users.
The Internet, however, is used for distributing electronic documents. There is also a need for paper documents because electronic documents are believed to be too transient or untrustworthy. For example, most experts find electronic voting to be untrustworthy without a paper trail. At the same time, a ballot is supposed to be secret. Therefore, paper ballots used in association with electronic voting systems exemplify one need for an encrypted paper document. Those skilled in the art of security documents are aware of many different applications calling for documents containing encrypted information.
Given printed documents with encrypted information, a key exchange technique is needed. An internet style technique with centralized certificate authorities is one possibility. Any type of centralized authority, however, immediately presents all the well understood problems inherent in every centralized system. Those problems include requiring permission from the authority before producing documents or decrypting information. Furthermore, all activity is governed by the procedures and failings of the central authority. Yet another argument is that a central authority controlling aspects of printed documents will have power over those documents and the users of those documents for the life of the documents. In many environments, such power is a liability. A need therefore exists for systems and methods for printing documents containing encrypted information and using those documents without having a centralized certificate authority.